Cryopumps are often employed to evacuate gases within process chambers. Typically, a cryopump is coupled to a process chamber by a conduit extending therebetween with a gate valve positioned within the conduit for enabling the cryopump to be isolated from the process chamber. One common situation in which the gate valve is closed to isolate the cryopump from the process chamber is to prevent particular gases or substances introduced into the process chamber from contaminating the cryopump. Another common situation in which the gate valve is closed is during regeneration of the cryopump where the cryopumping surfaces of the cryopump are warmed to release the gases trapped thereon, including hydrogen gas. Failure to close the gate valve during regeneration may allow the released hydrogen gas to enter the process chamber from the cryopump, thereby subjecting the hydrogen gas to the possibility of ignition.
The gate valves in some systems are controlled by a control system which has an interlock for locking the gate valve in particular situations, for example, during regeneration of the cryopump, during power outages, when high levels of particular gases or substances are within the process chamber, etc. Usually, the locked gate valves may be reopened by changing operating modes of the cryopump, or by using reset or override switches. Consequently, such gate valves may be opened during potentially dangerous or unsafe conditions, for example, when hydrogen gas is present within the cryopump. Opening of a gate valve with hydrogen gas present in the cryopump may result in an explosion or fire if the hydrogen gas flows into the process chamber and ignites.